Filtered oil in an air compressor of the type shown in U.S. Pat. No. 5,106,270 to Goettel, et al is not required for lubricating the bearings in the air compressor. However, it is believed that filtered oil will extend the service life of all lubricated parts as well as facilitate the use of rolling contact bearings in connecting rods and in wrist pin bosses of the high pressure and low pressure pistons in the air compressor taught in the referenced Goettel, et al patent.
The Goettel, et al air compressor employs an oil pump in the crankcase of the air compressor for supplying oil to the crankshaft and to the bearings of such air compressor. A hollow reciprocating shaft, or plunger, operates the pump by being connected at one end thereof to an eccentric journal located on the crankshaft, while the other end extends to the pump to provide alternate pumping cycles in the pump. The eccentric journal determines the stroke of the plunger and thus the capacity of the oil pump.
Low pressures of the alternate cycles draw oil from the crankcase into the pump. High pressures of the alternate cycles direct oil from the pump to the hollow plunger. From the hollow plunger oil flows to the eccentric journal and from the eccentric journal via drilled passages in the crankshaft to the bearings on the crankshaft, then to rifle drilled passages in the connecting rods to the connecting rod wrist pins; oil then returns to the crankcase.